Thermal equilibrium and efficient evaporation of an ultracold atom-molecule mixture

We derive the equilibrium conditions for a thermal atom-molecule mixture near a Feshbach resonance. Under the assumption of low collisional loss, thermodynamical properties are calculated and compared to the measurements of a recent experiment on fermionic lithium experiment. We discuss and evaluate possible collision mechanisms which can lead to atom-molecule conversion. Finally, we propose a novel evaporative cooling scheme to efficiently cool the molecules toward Bose-Einstein condensation

Creation of ultracold Sr2 molecules in the electronic ground state

We report on the creation of ultracold 84Sr2 molecules in the electronic ground state. The molecules are formed from atom pairs on sites of an optical lattice using stimulated Raman adiabatic passage (STIRAP). We achieve a transfer efficiency of 30% and obtain 4x10^4 molecules with full control over the external and internal quantum state. STIRAP is performed near the narrow 1S0-3P1 intercombination transition, using a vibrational level of the 0u potential as intermediate state. In preparation of our molecule association scheme, we have determined the binding energies of the last vibrational levels of the 0u, 1u excited-state, and the 1\Sigma_g^+ ground-state potentials. Our work overcomes the previous limitation of STIRAP schemes to systems with Feshbach resonances, thereby establishing a route that is applicable to many systems beyond bi-alkalis.Comment: 7 pages, 7 figures, 3 table

Two interacting particles at the metal-insulator transition

To investigate the influence of electronic interaction on the metal-insulator transition (MIT), we consider the Aubry-Andr\'{e} (or Harper) model which describes a quasiperiodic one-dimensional quantum system of non-interacting electrons and exhibits an MIT. For a two-particle system, we study the effect of a Hubbard interaction on the transition by means of the transfer-matrix method and finite-size scaling. In agreement with previous studies we find that the interaction localizes some states in the otherwise metallic phase of the system. Nevertheless, the MIT remains unaffected by the interaction. For a long-range interaction, many more states become localized for sufficiently large interaction strength and the MIT appears to shift towards smaller quasiperiodic potential strength.Comment: 26 RevTeX 3.0 pages with 10 EPS-figures include